The present invention relates to novel pigment preparations comprising
A) at least one organic or inorganic pigment and
B) at least one ethoxylated and propoxylated and/or butoxylated polyethyleneimine.
This invention further relates to the use of these pigment preparations for producing aqueous pigment dispersions, inks, including printing inks, and paints and also to pigment preparations for the ink-jet process.
The use of pigments, i.e., colorants that are insoluble in the application medium, generally requires the presence of dispersants, since pigment particles are subject to mutual forces of attraction and so tend to agglomerate or flocculate, which manifests itself through higher viscosities or worse color properties, especially insufficient color strength or lack of brilliance. Dispersants have a surface-active effect and so substantially lower the interfacial tension between the particles and also the dispersing work needed to subdivide particles.
Inks for the ink-jet process require particularly good dispersing of the pigment particles and stabilization of the pigment dispersion so that cloggage of the printer nozzles during printing as well as nonprinting times may be avoided and adequate stability in storage may be ensured. Special requirements also apply to the production of carbon black dispersions, since carbon black particles are generally even finer than color pigments.
WO-A-99/38053 discloses ink-jet inks based on carbon black pigments surface-modified by organic groups and containing hydroxyethylated, ethoxylated, hydroxypropylated or nonderivatized polyethyleneimines to improve wetfastness.
JP-A-060 352/1998 discloses overhead projector foil ink-jet inks containing nonmodified polyethyleneimines or polyacrylic acid/polyethyleneimine copolymers to fix the print on the foils as well as an acrylate-based dispersant.
It is an object of the present invention to provide novel pigment preparations having advantageous application properties in the production of aqueous pigment dispersions, inks, including printing inks, especially ink-jet inks, and coatings in the ink-jet process and not requiring any additional modification of the pigment surface or the presence of further assistants.
We have found that this object is achieved by the pigment preparations defined at the beginning.
Pigment preparations according to the invention include an organic or inorganic pigment as component (A). The term xe2x80x9corganic pigmentxe2x80x9d as used herein also comprehends vat dyes. It will be appreciated that pigment preparations according to the invention may also include mixtures of different organic or different inorganic pigments or organic and inorganic pigments.
Examples of suitable pigments (A) are:
Preferred pigments in this context are monoazo pigments (especially laked BONS pigments, naphthol AS pigments), disazo pigments (especially diaryl yellow pigments, bisacetoacetanilide pigments, disazopyrazolone pigments), quinacridone pigments, quinophthalone pigments, perinone pigments, phthalocyanine pigments, triarylcarbonium pigments (alkali blue pigments, laked rhodamines, dye salts with complex anions), isoindoline pigments and carbon blacks (in particular gas blacks or furnace blacks).
Examples of particularly preferred pigments are specifically: C.I. Pigment Yellow 138, C.I. Pigment Red 122, C.I. Pigment Violet 19, C.I. Pigment Blue 15:3 and 15:4, C.I. Pigment Black 7, C.I. Pigment Orange 5, 38 and 43 and C.I. Pigment Green 7.
Pigment preparations according to the invention include as component (B) one or more ethoxylated and propoxylated or ethoxylated and butoxylated or ethoxylated, propoxylated and butoxylated polyethyleneimine dispersants.
Preferably the polyethyleneimine was initially propoxylated or butoxylated and then ethoxylated.
Preference is given to polyethyleneimines (B) containing from 1 to 10 mol, especially from 1 to 6 mol, in particular from 2 to 5 mol, of propylene oxide or butylene oxide units per mole of NH function.
The ethylene oxide content of the polyethyleneimines (B) is preferably from 10 to 40 mol, particularly preferably from 15 to 35 mol, very particularly preferably from 20 to 30 mol, of ethylene oxide units per mole of NH function.
Particularly useful polyethyleneimines contain at least 12, especially from 20 to 45, in particular from 25 to 40, mol of alkylene oxide units per mole.
Generally the polyethyleneimine forming component (B) had a pre-alkoxylation average molecular weight Mw of from 600 to 25 000 g/mol, preferably from 1200 to 20 000 g/mol, particularly preferably from 2000 to 5000 g/mol, very particularly preferably of about 3000 g/mol.
The polyethyleneimines (B) are known from WO-A-99/67352 and can be prepared as described therein.
The pigment preparations of the present invention typically contain, based on the weight of pigment (A), from 5 to 200% by weight, especially from 20 to 100% by weight, of dispersant (B).
The dispersant (B) provides durable stabilization of very finely divided pigment dispersions, including in particular very finely divided carbon black dispersions. Generally 95%, preferably 99%, of pigment particles (A) have a particle size xe2x89xa61 xcexcm, preferably xe2x89xa60.5 xcexcm.
The pigment preparations of the present invention are very useful for producing aqueous pigment dispersions, waterborne inks (writing inks and especially ink-jet inks), solventborne inks, paints and toners.
Preferably pigment (A) and dispersant (B) are mixed with each other in the particular application medium. In the case of liquid application media, dispersing is advantageously effected using dissolvers (predispersing) and ball mills (fine dispersing), such as bead mills, high performance mills with small grinding media, e.g., double bead cylinder bead mills, and centrifugal fluidized bed mills.
The pigment preparations of the present invention are particularly useful for producing ink-jet inks.
The similarly inventive pigment preparations for the ink-jet process (hereinafter ink-jet inks for short) comprise
A) at least one organic or inorganic pigment,
B) at least one dispersant based on ethoxylated and propoxylated and/or butoxylated polyethyleneimine, and
C) an aqueous ink medium.
The aqueous ink medium (C) includes as its main component water (C1), preferably present mixed with one or more high-boiling (i.e., boiling point generally  greater than 100xc2x0 C.) and hence water-retaining organic solvents (C2) that are soluble in or miscible with water.
The organic solvent (C2) preferably comprises one or more solvents selected from the group consisting of polytetrahydrofuran having an average molecular weight M, of from 150 to 500 g/mol, polyhydric alcohols, polyethylene glycols, polypropylene glycols, polyethylene glycol monoalkyl ethers, polypropylene glycol monoalkyl ethers, pyrrolidone and N-alkylpyrrolidones.
Particularly useful ink-jet inks according to the invention include polytetrahydrofuran as constituent of the organic solvent component (C2). Polytetrahydrofurans having an average molecular weight Mw of from 200 to 300 g/mol are preferred and of about 250 g/mol (corresponding to a molecular weight distribution from 225 to 275 g/mol; Poly-THF 250, BASF) are particularly preferred.
The polytetrahydrofuran may be prepared in known manner by cationic polymerization of tetrahydrofuran. The products are linear polytetramethylene glycols.
The polytetrahydrofuran may be mixed with one or more (e.g., two, three or four) organic solvents.
Useful organic solvents (C2) further include polyhydric alcohols, preferably branched and unbranched polyhydric alcohols containing from 2 to 8, especially from 3 to 6, carbon atoms, such as ethylene glycol, 1,2- and 1,3-propylene glycol, glycerol, erythritol, pentaerythritol, pentitols such as arabitol, adonitol and xylitol and hexitols such as sorbitol, mannitol and dulcitol.
Useful solvents (C2) further include polyethylene glycols and polypropylene glycols (which is also to be understood as meaning the lower polymers (di-, tri- and tetramers)) and their mono (especially C1-C6, in particular C1-C4) alkyl ethers. Preference is given to polyethylene and polypropylene glycols having average molecular weights of from 100 to 1500 g/mol, in particular from 200 to 800 g/mol, especially from 300 to 500 g/mol. Examples are diethylene glycol, triethylene glycol, tetraethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, di-, tri- and tetra-1,2- and -1,3-propylene glycol and di-, tri- and tetra-1,2- and -1,3-propylene glycol monomethyl, monoethyl, monopropyl and monobutyl ether.
Useful solvents (C2) further include pyrrolidone and N-alkylpyrrolidones whose alkyl chain preferably contains from 1 to 4, especially 1 or 2, carbon atoms. Examples of useful alkylpyrrolidones are N-methylpyrrolidone, N-ethylpyrrolidone and N-(2-hydroxyethyl)pyrrolidone.
Examples of particularly preferred solvents (C2) are the polytetrahydrofurans described above, 1,2-propylene glycol, 1,3-propylene glycol, glycerol, sorbitol, diethylene glycol, polyethylene glycol (M, 300-500 g/mol), diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, pyrrolidone, N-methylpyrrolidone and N-(2-hydroxyethyl)pyrrolidone.
The solvent component (C2) may advantageously be supplemented with urea (generally in amounts from 0.5 to 3% by weight, based on the weight of the ink-jet ink) to further reinforce the water-containing effect of the solvent mixture (C2).
The ink-jet inks of the present invention include generally from 0.1 to 40% by weight, preferably from 5 to 30% by weight, particularly preferably from 10 to 25% by weight, very particularly preferably from 10 to 20% by weight, of organic solvent component (C2).
Preference is given to using a mixture of organic solvents (C2) in which the weight ratio of polytetrahydrofuran to further solvent is in the range from 1:20 to 1:1. Ink-jet inks according to the invention accordingly include preferably from 0.5 to 20% by weight, especially from 1 to 10% by weight, of polytetrahydrofuran and from 1 to 30% by weight, especially from 1 to 20% by weight, of further solvent (C2).
Water is the main constituent (C1) of ink-jet inks according to the invention. The water content is customarily in the range from 50 to 95% by weight, preferably in the range from 60 to 80% by weight.
The pigment (A) is generally present in the ink-jet inks of the present invention in amounts of generally from 0.01 to 20% by weight, preferably from 0.2 to 10% by weight, particularly preferably from 1 to 6% by weight.
The ink-jet inks of the present invention further include generally from 0.1 to 25% by weight, preferably from 0.5 to 10% by weight, of dispersant (B).
It will be appreciated that the ink-jet inks of the present invention may include further assistants of the type which are customary especially for (aqueous) ink-jet inks and in the printing and coatings industry. Examples of such assistants include preservatives (such as 1,2-benzisothiazolin-3-one and its alkali metal salts, glutaraldehyde and/or tetramethylolacetylenediurea), antioxidants, degassers/defoamers (such as acetylenediols and ethoxylated acetylenediols, which customarily contain from 20 to 40 mol of ethylene oxide per mole of acetylenediol and also have a dispersing effect), viscosity regulators, flow agents, wetters which can be used in amounts of from 0.5 to 5% by weight to reduce the surface tension of the ink (e.g., wetting surfactants based on ethoxylated or propoxylated fatty or oxo alcohols, propylene oxide/ethylene oxide block copolymers, ethoxylates of oleic acid or alkylphenols, alkylphenol ether sulfates, alkylpolyglycosides, alkyl phosphonates, alkylphenyl phosphonates, alkyl phosphates, alkylphenyl phosphates), anti-settlers, luster improvers, lubricants, adhesion improvers, anti-skinning agents, delusterants, emulsifiers, stabilizers, water repellents, light control additives, hand improvers, antistats and bases such as triethanolamine to regulate the pH. When these agents are part of ink-jet inks according to the invention, their total amount is generally xe2x89xa65% by weight, especially xe2x89xa62% by weight, in particular xe2x89xa61% by weight, based on the weight of the ink-jet ink.
The ink-jet inks of the present invention customarily have a dynamic viscosity of from 1 to 5 mm2/sec, preferably from 1 to 3 mm2/sec.
The surface tension of the ink-jet inks of the present invention is generally in the range from 20 to 70 mN/m, preferably from 25 to 40 mN/m. The pH of the ink-jet inks-of the present invention is generally in the range from 5 to 10, preferably from 7 to 9.
Ink-jet inks according to the invention are advantageously prepared as follows:
The pigment (A), for example in the form of an aqueous presscake, is mixed together with the dispersant (B) in the presence of water and dispersed in a suitable apparatus. The resulting mixture is then ground in a mill to the desired particle size distribution (generally xe2x89xa61 xcexcm, preferably xe2x89xa60.5 xcexcm). After the desired colorant concentration has been set by addition of solvent (C2), water and optionally further assistants, the preparation is filtered using a filtering means with fines removal within the range from 1 to 0.5 xcexcm.
The ink-jet inks of the invention can be used with advantage for printing sheetlike or three-dimensionally configured substrates by the ink-jet process, which comprises printing the ink-let inks onto the substrate and if desired subsequently fixing the print obtained.
In the ink-jet process, the typically aqueous inks are sprayed in small droplets directly onto the substrate. There is a continuous form of the process, in which the ink is pressed at a uniform rate through a nozzle and the jet is directed onto the substrate by an electric field depending on the pattern to be printed, and there is an interrupted or drop-on-demand process, in which the ink is expelled only where a colored dot is to appear, the latter form of the process employing either a piezoelectric crystal or a heated hollow needle (bubble or thermal jet process) to exert pressure on the ink system and so eject an ink droplet. These techniques are described in Text. Chem. Color 19 (1987), No. 8, 23-29, and 21 (1989), No. 6, 27-32.
The ink-jet inks of the invention are particularly useful as inks for the bubble jet process or the process employing a piezoelectric crystal.
If the print is to be fixed, this may be done in a known manner and as described in WO-A-99/01516 by, for example, applying a binder, if desired in the form of a dispersion or emulsion, to the printed substrate and curing the binder or laminating on a film.
Further details concerning these binders are to be found in WO-A-99/01516.
The ink-jet inks of the invention may be printed on all types of substrate materials. Examples of substrate materials include
coated or uncoated cellulosics such as paper, paperboard, cardboard, wood and woodbase,
coated or uncoated metallic materials such as foils, sheets or workpieces composed of aluminum, iron, copper, silver, gold, zinc or alloys thereof,
coated or uncoated silicatic materials such as glass, porcelain and ceramics,
polymeric materials of any kind such as polystyrene, polyamides, polyesters, polyethylene, polypropylene, melamine resins, polyacrylates, polyacrylonitrile, polyurethanes, polycarbonates, polyvinyl chloride, polyvinyl alcohols, polyvinyl acetates, polyvinylpyrrolidones and corresponding copolymers and block copolymers, biodegradable polymers and natural polymers such as gelatin,
textile materials such as fibers, yarns, threads, knits, wovens, nonwovens and garments composed of polyester, modified polyester, polyester blend fabrics, cellulosics such as cotton, cotton blend fabrics, jute, flax, hemp and ramie, viscose, wool, silk, polyamide, polyamide blend fabrics, polyacrylonitrile, triacetate, acetate, polycarbonate, polypropylene, polyvinyl chloride, polyester microfibers and glass fiber fabric,
leatherxe2x80x94both natural and artificialxe2x80x94in the form of smooth leather, nappa leather or suede leather,
comestibles and cosmetics.
The substrate material may be sheetlike or three-dimensional in configuration and may be printed with the ink-jet inks of the invention both uniformly and imagewise.
Ink-jet inks according to the invention have altogether advantageous application properties, especially good start-of-print behavior, good sustained use behavior (kogation) and good storage stability, producing prints of high quality, i.e., brilliance and depth of shade, and also high rubfastness, lightfastness, waterfastness and wetrubfastness. They are particularly useful for printing coated and uncoated paper.